Silibinin

Silibinin

Clinical data
AHFS/Drugs.com	International Drug Names
Routes of administration	Oral Intravenous
ATC code	A05BA03 (WHO)
Identifiers
IUPAC name (2R,3R)-3,5,7-trihydroxy- 2-[(2R,3R)-3-(4-hydroxy-3-methoxyphenyl)-2-(hydroxymethyl) -2,3-dihydrobenzo[b][1,4]dioxin-6-yl]chroman-4-one
CAS Number	22888-70-6 N
PubChem (CID)	31553
ChemSpider	29263 Y
UNII	4RKY41TBTF Y
KEGG	D08515 Y
ChEBI	CHEBI:9144 N
ChEMBL	CHEMBL9509 N
ECHA InfoCard	100.041.168
Chemical and physical data
Formula	C25H22O10
Molar mass	482.44 g/mol
3D model (Jmol)	Interactive image
SMILES O=C4c5c(O)cc(O)cc5O[C@H](c2ccc1O[C@@H]([C@H](Oc1c2)c3ccc(O)c(OC)c3)CO)[C@H]4O
InChI InChI=1S/C25H22O10/c1-32-17-6-11(2-4-14(17)28)24-20(10-26)33-16-5-3-12(7-18(16)34-24)25-23(31)22(30)21-15(29)8-13(27)9-19(21)35-25/h2-9,20,23-29,31H,10H2,1H3/t20-,23+,24-,25-/m1/s1 Y Key:SEBFKMXJBCUCAI-HKTJVKLFSA-N Y
NY (what is this?)

Silibinin (INN), also known as silybin (both from Silybum, the generic name of the plant from which it is extracted), is the major active constituent of silymarin, a standardized extract of the milk thistle seeds, containing a mixture of flavonolignans consisting of silibinin, isosilibinin, silicristin, silidianin, and others. Silibinin itself is mixture of two diastereomers, silybin A and silybin B, in approximately equimolar ratio. The mixture exhibits a number of pharmacological effects, particularly in the liver, and there is some clinical evidence for the use of silibinin as a supportive element in alcoholic and child grade 'A' liver cirrhosis.

Poor water solubility and bioavailability of silymarin led to the development of enhanced formulations. Silipide (trade name Siliphos), a complex of silymarin and phosphatidylcholine (lecithin), is about 10 times more bioavailable than silymarin. An earlier study had concluded Siliphos to have 4.6 fold higher bioavailability. It has been also reported that silymarin inclusion complex with β-cyclodextrin is much more soluble than silymarin itself. There have also been prepared glycosides of silybin, which show better water solubility and even stronger hepatoprotective effect.

Silymarin, as other flavonoids, has been shown to inhibit P-glycoprotein-mediated cellular efflux. The modulation of P-glycoprotein activity may result in altered absorption and bioavailability of drugs that are P-glycoprotein substrates. It has been reported that silymarin inhibits enzymes and an interaction with drugs primarily cleared by P450s cannot be excluded.

A phase I clinical trial in humans with prostate cancer designed to study the effects of high dose silibinin found 13 grams daily to be well tolerated in patients with advanced prostate cancer with asymptomatic liver toxicity (hyperbilirubinemia and elevation of alanine aminotransferase) being the most commonly seen adverse event.